package org.apache.maven;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

import java.util.ArrayList;
import java.util.Collection;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.Map;

import org.apache.maven.execution.ProjectDependencyGraph;
import org.apache.maven.project.MavenProject;

/**
 * Provides a sub view of another dependency graph.
 * 
 * @author Benjamin Bentmann
 */
class FilteredProjectDependencyGraph implements ProjectDependencyGraph {

  private ProjectDependencyGraph projectDependencyGraph;

  private Map<MavenProject, ?> whiteList;

  private List<MavenProject> sortedProjects;

  /**
   * Creates a new project dependency graph from the specified graph.
   * 
   * @param projectDependencyGraph The project dependency graph to create a sub view from, must not
   *        be {@code null}.
   * @param whiteList The projects on which the dependency view should focus, must not be
   *        {@code null}.
   */
  public FilteredProjectDependencyGraph(ProjectDependencyGraph projectDependencyGraph, Collection<? extends MavenProject> whiteList) {
    if (projectDependencyGraph == null) {
      throw new IllegalArgumentException("project dependency graph missing");
    }

    this.projectDependencyGraph = projectDependencyGraph;

    this.whiteList = new IdentityHashMap<MavenProject, Object>();

    for (MavenProject project : whiteList) {
      this.whiteList.put(project, null);
    }
  }

  public List<MavenProject> getSortedProjects() {
    if (sortedProjects == null) {
      sortedProjects = applyFilter(projectDependencyGraph.getSortedProjects());
    }

    return new ArrayList<MavenProject>(sortedProjects);
  }

  public List<MavenProject> getDownstreamProjects(MavenProject project, boolean transitive) {
    return applyFilter(projectDependencyGraph.getDownstreamProjects(project, transitive));
  }

  public List<MavenProject> getUpstreamProjects(MavenProject project, boolean transitive) {
    return applyFilter(projectDependencyGraph.getUpstreamProjects(project, transitive));
  }

  private List<MavenProject> applyFilter(Collection<? extends MavenProject> projects) {
    List<MavenProject> filtered = new ArrayList<MavenProject>(projects.size());

    for (MavenProject project : projects) {
      if (whiteList.containsKey(project)) {
        filtered.add(project);
      }
    }

    return filtered;
  }

  @Override
  public String toString() {
    return getSortedProjects().toString();
  }

}
